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This article has been withdrawn as it was published elsewhere and accidentally duplicated. The original article can be seen here: 10.1108/00368790510614163. When citing the article, please cite: B.S. Yilbas, M. Sunar, Z. Qasem, B.J. Abdul Aleem, S. Zainaulabdeen, (2005), “Study into mechanical properties of TiN coating on Ti-6Al-4V alloy through three-point bending tests”, Industrial Lubrication and Tribology, Vol. 57 Iss: 5, pp. 193 - 196.

The purpose of this paper is to consider the corrosion properties of laser nitrided Ti‐6Al‐4V alloys that have been reported previously by several researchers.

Different kinds of surface nitriding methods of titanium alloys, such as plasma nitriding, ion nitriding, gas and laser nitriding, are introduced. Microstructure changes, such as phase formation and the influence of laser processing parameters in laser nitriding layers of Ti‐6Al‐4V alloys, were investigated using scanning electron microscope, transmission electron microscope, X‐ray photo‐electron spectroscopy, and X‐ray diffraction. Based on investigations presented in the literature, the effect of laser nitriding on the corrosion behavior of Ti‐6Al‐4V alloy was reviewed.

By regulating the laser processing parameter, the microstructure of the nitrided layer can be controlled to optimize corrosion properties. This layer improves corrosion behavior in most environments, due to the formation of a continuous TiNxOy passive film, which can retard the ingress of corrosive ions into the substrate and can maintain a constant value of a current density. Therefore, the laser gas nitrided specimens have a relatively noble corrosion potential and a very small corrosion current, as compared to untreated specimens.

This paper comprises a critical review, and its collection of references is useful. It summarizes current knowledge in laser surface treatment research.

A model study of laser heating process including phase change and molten flow in the melt pool gives physical insight into the process and provides useful information on the influence of melting parameters. In addition, the predictions reduce the experimental cost and minimize the experimental time. Consequently, investigation into laser control melting of the titanium alloy becomes essential. The purpose of this paper is to do this.

Laser repetitive pulse heating of titanium surface is investigated and temperature field as well as Marangoni flow in the melt pool is predicted using finite volume approach. The influence of laser scanning speed and laser pulse parameter (defining the laser pulse intensity distribution at the workpiece surface) on temperature distribution and melt size is examined. The experiment is carried out to validate temperature predictions for two consecutive laser pulses.

The influence of laser scanning speed is significant on the melt pool geometry, which is more pronounced for the laser pulse parameter β=0. Temperature predictions agree with the thermocouple data obtained from the experiment.

Although temperature dependent properties are used in the simulations, isotropy in properties may limit the simulations. The laser canning speed is limited to 0.3 m/s, which is good for surface treatment process, but it may slow for annealing treatments.

The results are very useful to capture insight into the melting process. In addition, the influence of laser scanning speed and laser pulse intensity distribution on the melt formation in the surface vicinity is well presented, which will be useful for those working on laser surface treatment process.

The work is original and findings are new, which demonstrate the influence of laser parameters on the melt pool formation and resulting Marangoni flow.

The purpose of this paper is to investigate the morphological and metallurgical changes of laser gas‐assisted nitriding of titanium implants.

Laser gas‐assisted nitriding of titanium implant is carried out and the metallurgical as well as the morphological changes in the nitride layer are examined using optical microscopy, SEM, XRD, and X‐ray photoelectron spectroscopy. Temperature and thermal stress fields are computed during the laser heating process adopting the finite element method. The residual stress formed in the nitride layer is measured using the XRD technique while micro‐indentation tests are carried out to determine the fracture toughness of the surface after the laser treatment process.

It is found that nitride depth layer extends to 40 μm below the surface and it is free from the cracks and micro‐voids. The residual stress formed on the surface region is higher than at some depth below the surface in the nitride layer, provided that the maximum residual stress is less than the elastic limit of the substrate material.

The paper contains original findings and the findings are not submitted any other journal for publication.

The purpose of this paper is to investigate the heat transfer rates from the kerf surfaces and skin friction at the kerf wall due to the jet impingement in relation to laser cutting process.

Three‐dimensional modeling for the flow and heat transfer analysis is considered. The numerical scheme using the control volume approach is introduced to solve the governing equations of flow and heat transfer. The k‐w turbulence model is incorporated to account for the turbulence.

It is found that the Nusselt number and the skin friction remains high in the region next to the kerf inlet and it decreases towards the kerf exit for all kerf thicknesses considered. The flow acceleration in the kerf also results in the second peak of the Nusselt number and the skin friction.

The melting at the kerf surface was omitted and the constant temperature boundary representing the melt surface is incorporated in the analysis. However, care was taken during the mesh generation to avoid grid dependent solutions.

The findings and discussions provide the useful information on the practical laser cutting process, in particular, physical insight into the effect of the kerf thickness on the heat transfer and skin friction.

No previous work has been carried out in three‐dimensional space to predict the heat transfer and skin friction, which are important for practical laser cutting applications. Therefore, the work reported is original.

To investigate the influence of conical and annular nozzle geometric configurations on the flow structure and heat transfer characteristics near the stagnation point of a flat plate with limited heated area.

The conical and annular conical nozzles were designed such that the exit area of both nozzles is the same and the mass flow rate passing through the nozzles is kept constant for both nozzles. The governing equations of flow and heat transfer are modeled numerically using a control volume approach. The grid independent solutions are secured and the predictions of flow and heat transfer characteristics are compared with the simple pipe flow with the same area and mass flow rate. The Reynolds stress turbulence model is employed to account for the turbulence. A flat plate with a limited heated area is accommodated to resemble the laser heating situations and air is used as assisting gas.

It is found that nozzle exiting velocity profiles differ considerably with changing the nozzle cone angle. Increasing nozzle cone angle enhances the radial flow and extends the stagnation zone away from the plate surface. The impinging jet with a fully developed velocity profile results in enhanced radial acceleration of the flow. Moreover, the flow structure changes considerably for annular conical and conical nozzles. The nozzle exiting velocity profile results in improved heat transfer coefficient at the flat plate surface. However, the achievement of fully developed pipe flow like velocity profile emanating from a nozzle is almost impossible for practical laser applications. Therefore, use of annular conical nozzles facilitates the high cooling rates from the surface during laser heating process

The results are limited with theoretical predictions due to the difficulties arising in experimental studies.

The results can be used in laser machining applications to improve the end product quality. It also enables selection of the appropriate nozzle geometry for a particular machining application.

This paper provides information on the flow and heat transfer characteristics associated with the nozzle geometric configurations and offers practical help for the researchers and scientists working in the laser machining area.

The paper's aim is to provide information on heat transfer and flow characteristics for a jet emerging from a conical nozzle and impinging onto the cylindrical, which resembles the laser heating process, for researchers and graduate students working in the laser processing area, which can help them to improve the understanding of the laser machining process.

A numerical scheme employing the control volume approach is introduced to model the flow and heating situations. The effect of jet velocity on the heat transfer rates and skin friction around the cylindrical cavity subjected to the jet impingement was investigated.

Increasing jet velocity at nozzle exit enhances the heat transfer rates from the cavity wall and modifies the skin friction at cavity wall, which is more pronounced as the cavity depth increases to 1 mm.

The effects of nozzle cone angle on the flow structure and heat transfer characteristics were not examined, which perhaps limits the general usefulness of the findings.

Very useful information are provided for the laser gas assisted processing, which has a practical importance in machining industry.

This paper provides original information for the effects of the gas jet velocity on the cooling rates of the laser produced cavity.

Inconel 617 alloy is widely used in industry due to its superior high temperature properties. After long periods of operation, the alloy microstructure changes. One of the methods to regain the alloy microstructure is heat treatment at elevated temperatures. In the present study, electrochemical and mechanical responses of Inconel 617 alloy over 30,000 hours of operation as a transition‐piece in agas turbine engine are examined. The heat treatment process at two different temperature levels is applied when refurbishing the alloy microstructure. The electrochemical tests are conducted to investigate the corrosion response of the alloy before and after the heat treatment process. Fatigue and tensile tests are carried out for the workpieces subjected to the electrochemical tests. SEM is introduced to examine the fractured surfaces.

The gas assisted Iaser heating of engineering surfaces finds wide application in industry. Numerical simulation of the heating process may considerably reduce the cost spent on experimentation. In the present study, 2‐dimensional axisymmetric flow and energy equations are solved numerically using a control volume approach for the case of a gas assisted laser heating of steel surfaces. Various turbulence models including standard k‐ε, k‐ε YAP, low Reynolds number k‐ε and RSTM models are tested. The low Reynolds number k‐ε model is selected to account for the turbulence. Variable properties of both solid and gas are taken into account during the simulation. Air is considered as an assisting gas impinging the workpiece surface coaxially with the laser beam. In order to validate the presently considered methodology, the study is extended to include comparison of present predictions with analytical solution for the case available in the literature. It is found that the assisting gas jet has some influence on the temperature profiles. This effect is minimum at the irradiated spot center and it amplifies considerably in the gas side. In addition, account for the variable properties results in lower surface temperatures as compared to the constant properties case.

Jet impingement onto surface finds wide application in industry. In laser processing an assisting gas jet is introduced either to shield the surface from oxidation reactions or initiating exothermic reaction to increase energy in the region irradiated by a laser beam. When an impinging gas jet is used for a shielding purpose, the gas jet enhances the convective cooling of the cavity surface. The convective cooling of the laser formed cavity surface can be simulated through jet impingement onto a cavity with elevated wall temperatures. In the present study, gas impingement onto a slot is considered. The wall temperature of the cavity is kept at elevated temperature similar to the melting temperature of the substrate material. A control volume approach is used to simulate the flow and temperature fields. The Reynolds Stress Turbulence model (RSTM) is employed to account for the turbulence. To examine the effect of cavity depth on the heat transfer characteristics, the depth is varied while keeping the cavity width constant. It is found that impinging jet penetrates into a cavity, which in turn, results in a stagnation region extending into the cavity. An impinging gas jet has considerable effect on the Nusselt number along the side walls of the cavity while the Nusselt number monotonically changes with varying cavity depth.